4-17 Figure 4-14.Zone of mutual visibility. Q13. What are the two limitations to an active satellite communications system? FUTURE SATELLITE COMMUNICATIONS Satellite communications are becoming well established in the Navy. In October 1983 the Department of the Navy established the Naval Space Command, which assumed operational responsibility for Navy space systems plus coordination responsibility with other operational activities. Most ships have satellite communications capability. New systems have been installed on ships and are fully compatible with other electronic systems and equipment. Communications via satellite has increased existing Navy communications capabilities for the command and control of naval forces. Satellite communications has not replaced all existing means of radio communications. However, it is a major step in modernizing Navy communications. It has relieved the Navy of its total dependence on hf radio transmission and reduced the need for many hf ground stations overseas. A recent step in the advancement of satellite communications was the start of the DSCS Phase III. The first Phase III satellite was launched into orbit by the space shuttle in the summer of 1984. Seven satellites will be placed in space during this phase. Figure 4-15 shows a Phase III satellite being tested in a simulated space environment, Figure 4-16 shows the Phase III satellite as it appears in space. Phase III will develop the use of 40-watt, solid-state amplifiers to replace the currently used traveling-wave tube (twt). It will also be used to develop new type filters. These filters will provide increased channel bandwidth, which will provide additional communications capacity.